If you are happy with your current Sony pre-pro 5.1 set up and don't plan on adding any more speakers. I don't see any reason to attempt an upgrade.
Know since of going 7, 9 or 11 channels when you can't use it now. Sounds like you really like how your system is now. If it ain't broke, let it be until you are able to go with more channels. When the time comes you are able to add more speakers, by then there will be the next newer feature set thing on the market.
I think just like most audio listeners, your just itching to buy something new, when you don't really need it.
Edited: meat-hook fingers pressing wrong keys LOL